1 /* 2 * Compressed RAM block device 3 * 4 * Copyright (C) 2008, 2009, 2010 Nitin Gupta 5 * 2012, 2013 Minchan Kim 6 * 7 * This code is released using a dual license strategy: BSD/GPL 8 * You can choose the licence that better fits your requirements. 9 * 10 * Released under the terms of 3-clause BSD License 11 * Released under the terms of GNU General Public License Version 2.0 12 * 13 */ 14 15 #define KMSG_COMPONENT "zram" 16 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt 17 18 #include <linux/module.h> 19 #include <linux/kernel.h> 20 #include <linux/bio.h> 21 #include <linux/bitops.h> 22 #include <linux/blkdev.h> 23 #include <linux/buffer_head.h> 24 #include <linux/device.h> 25 #include <linux/genhd.h> 26 #include <linux/highmem.h> 27 #include <linux/slab.h> 28 #include <linux/backing-dev.h> 29 #include <linux/string.h> 30 #include <linux/vmalloc.h> 31 #include <linux/err.h> 32 #include <linux/idr.h> 33 #include <linux/sysfs.h> 34 #include <linux/debugfs.h> 35 #include <linux/cpuhotplug.h> 36 #include <linux/part_stat.h> 37 38 #include "zram_drv.h" 39 40 static DEFINE_IDR(zram_index_idr); 41 /* idr index must be protected */ 42 static DEFINE_MUTEX(zram_index_mutex); 43 44 static int zram_major; 45 static const char *default_compressor = "lzo-rle"; 46 47 /* Module params (documentation at end) */ 48 static unsigned int num_devices = 1; 49 /* 50 * Pages that compress to sizes equals or greater than this are stored 51 * uncompressed in memory. 52 */ 53 static size_t huge_class_size; 54 55 static void zram_free_page(struct zram *zram, size_t index); 56 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, 57 u32 index, int offset, struct bio *bio); 58 59 60 static int zram_slot_trylock(struct zram *zram, u32 index) 61 { 62 return bit_spin_trylock(ZRAM_LOCK, &zram->table[index].flags); 63 } 64 65 static void zram_slot_lock(struct zram *zram, u32 index) 66 { 67 bit_spin_lock(ZRAM_LOCK, &zram->table[index].flags); 68 } 69 70 static void zram_slot_unlock(struct zram *zram, u32 index) 71 { 72 bit_spin_unlock(ZRAM_LOCK, &zram->table[index].flags); 73 } 74 75 static inline bool init_done(struct zram *zram) 76 { 77 return zram->disksize; 78 } 79 80 static inline struct zram *dev_to_zram(struct device *dev) 81 { 82 return (struct zram *)dev_to_disk(dev)->private_data; 83 } 84 85 static unsigned long zram_get_handle(struct zram *zram, u32 index) 86 { 87 return zram->table[index].handle; 88 } 89 90 static void zram_set_handle(struct zram *zram, u32 index, unsigned long handle) 91 { 92 zram->table[index].handle = handle; 93 } 94 95 /* flag operations require table entry bit_spin_lock() being held */ 96 static bool zram_test_flag(struct zram *zram, u32 index, 97 enum zram_pageflags flag) 98 { 99 return zram->table[index].flags & BIT(flag); 100 } 101 102 static void zram_set_flag(struct zram *zram, u32 index, 103 enum zram_pageflags flag) 104 { 105 zram->table[index].flags |= BIT(flag); 106 } 107 108 static void zram_clear_flag(struct zram *zram, u32 index, 109 enum zram_pageflags flag) 110 { 111 zram->table[index].flags &= ~BIT(flag); 112 } 113 114 static inline void zram_set_element(struct zram *zram, u32 index, 115 unsigned long element) 116 { 117 zram->table[index].element = element; 118 } 119 120 static unsigned long zram_get_element(struct zram *zram, u32 index) 121 { 122 return zram->table[index].element; 123 } 124 125 static size_t zram_get_obj_size(struct zram *zram, u32 index) 126 { 127 return zram->table[index].flags & (BIT(ZRAM_FLAG_SHIFT) - 1); 128 } 129 130 static void zram_set_obj_size(struct zram *zram, 131 u32 index, size_t size) 132 { 133 unsigned long flags = zram->table[index].flags >> ZRAM_FLAG_SHIFT; 134 135 zram->table[index].flags = (flags << ZRAM_FLAG_SHIFT) | size; 136 } 137 138 static inline bool zram_allocated(struct zram *zram, u32 index) 139 { 140 return zram_get_obj_size(zram, index) || 141 zram_test_flag(zram, index, ZRAM_SAME) || 142 zram_test_flag(zram, index, ZRAM_WB); 143 } 144 145 #if PAGE_SIZE != 4096 146 static inline bool is_partial_io(struct bio_vec *bvec) 147 { 148 return bvec->bv_len != PAGE_SIZE; 149 } 150 #else 151 static inline bool is_partial_io(struct bio_vec *bvec) 152 { 153 return false; 154 } 155 #endif 156 157 /* 158 * Check if request is within bounds and aligned on zram logical blocks. 159 */ 160 static inline bool valid_io_request(struct zram *zram, 161 sector_t start, unsigned int size) 162 { 163 u64 end, bound; 164 165 /* unaligned request */ 166 if (unlikely(start & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1))) 167 return false; 168 if (unlikely(size & (ZRAM_LOGICAL_BLOCK_SIZE - 1))) 169 return false; 170 171 end = start + (size >> SECTOR_SHIFT); 172 bound = zram->disksize >> SECTOR_SHIFT; 173 /* out of range range */ 174 if (unlikely(start >= bound || end > bound || start > end)) 175 return false; 176 177 /* I/O request is valid */ 178 return true; 179 } 180 181 static void update_position(u32 *index, int *offset, struct bio_vec *bvec) 182 { 183 *index += (*offset + bvec->bv_len) / PAGE_SIZE; 184 *offset = (*offset + bvec->bv_len) % PAGE_SIZE; 185 } 186 187 static inline void update_used_max(struct zram *zram, 188 const unsigned long pages) 189 { 190 unsigned long old_max, cur_max; 191 192 old_max = atomic_long_read(&zram->stats.max_used_pages); 193 194 do { 195 cur_max = old_max; 196 if (pages > cur_max) 197 old_max = atomic_long_cmpxchg( 198 &zram->stats.max_used_pages, cur_max, pages); 199 } while (old_max != cur_max); 200 } 201 202 static inline void zram_fill_page(void *ptr, unsigned long len, 203 unsigned long value) 204 { 205 WARN_ON_ONCE(!IS_ALIGNED(len, sizeof(unsigned long))); 206 memset_l(ptr, value, len / sizeof(unsigned long)); 207 } 208 209 static bool page_same_filled(void *ptr, unsigned long *element) 210 { 211 unsigned long *page; 212 unsigned long val; 213 unsigned int pos, last_pos = PAGE_SIZE / sizeof(*page) - 1; 214 215 page = (unsigned long *)ptr; 216 val = page[0]; 217 218 if (val != page[last_pos]) 219 return false; 220 221 for (pos = 1; pos < last_pos; pos++) { 222 if (val != page[pos]) 223 return false; 224 } 225 226 *element = val; 227 228 return true; 229 } 230 231 static ssize_t initstate_show(struct device *dev, 232 struct device_attribute *attr, char *buf) 233 { 234 u32 val; 235 struct zram *zram = dev_to_zram(dev); 236 237 down_read(&zram->init_lock); 238 val = init_done(zram); 239 up_read(&zram->init_lock); 240 241 return scnprintf(buf, PAGE_SIZE, "%u\n", val); 242 } 243 244 static ssize_t disksize_show(struct device *dev, 245 struct device_attribute *attr, char *buf) 246 { 247 struct zram *zram = dev_to_zram(dev); 248 249 return scnprintf(buf, PAGE_SIZE, "%llu\n", zram->disksize); 250 } 251 252 static ssize_t mem_limit_store(struct device *dev, 253 struct device_attribute *attr, const char *buf, size_t len) 254 { 255 u64 limit; 256 char *tmp; 257 struct zram *zram = dev_to_zram(dev); 258 259 limit = memparse(buf, &tmp); 260 if (buf == tmp) /* no chars parsed, invalid input */ 261 return -EINVAL; 262 263 down_write(&zram->init_lock); 264 zram->limit_pages = PAGE_ALIGN(limit) >> PAGE_SHIFT; 265 up_write(&zram->init_lock); 266 267 return len; 268 } 269 270 static ssize_t mem_used_max_store(struct device *dev, 271 struct device_attribute *attr, const char *buf, size_t len) 272 { 273 int err; 274 unsigned long val; 275 struct zram *zram = dev_to_zram(dev); 276 277 err = kstrtoul(buf, 10, &val); 278 if (err || val != 0) 279 return -EINVAL; 280 281 down_read(&zram->init_lock); 282 if (init_done(zram)) { 283 atomic_long_set(&zram->stats.max_used_pages, 284 zs_get_total_pages(zram->mem_pool)); 285 } 286 up_read(&zram->init_lock); 287 288 return len; 289 } 290 291 static ssize_t idle_store(struct device *dev, 292 struct device_attribute *attr, const char *buf, size_t len) 293 { 294 struct zram *zram = dev_to_zram(dev); 295 unsigned long nr_pages = zram->disksize >> PAGE_SHIFT; 296 int index; 297 298 if (!sysfs_streq(buf, "all")) 299 return -EINVAL; 300 301 down_read(&zram->init_lock); 302 if (!init_done(zram)) { 303 up_read(&zram->init_lock); 304 return -EINVAL; 305 } 306 307 for (index = 0; index < nr_pages; index++) { 308 /* 309 * Do not mark ZRAM_UNDER_WB slot as ZRAM_IDLE to close race. 310 * See the comment in writeback_store. 311 */ 312 zram_slot_lock(zram, index); 313 if (zram_allocated(zram, index) && 314 !zram_test_flag(zram, index, ZRAM_UNDER_WB)) 315 zram_set_flag(zram, index, ZRAM_IDLE); 316 zram_slot_unlock(zram, index); 317 } 318 319 up_read(&zram->init_lock); 320 321 return len; 322 } 323 324 #ifdef CONFIG_ZRAM_WRITEBACK 325 static ssize_t writeback_limit_enable_store(struct device *dev, 326 struct device_attribute *attr, const char *buf, size_t len) 327 { 328 struct zram *zram = dev_to_zram(dev); 329 u64 val; 330 ssize_t ret = -EINVAL; 331 332 if (kstrtoull(buf, 10, &val)) 333 return ret; 334 335 down_read(&zram->init_lock); 336 spin_lock(&zram->wb_limit_lock); 337 zram->wb_limit_enable = val; 338 spin_unlock(&zram->wb_limit_lock); 339 up_read(&zram->init_lock); 340 ret = len; 341 342 return ret; 343 } 344 345 static ssize_t writeback_limit_enable_show(struct device *dev, 346 struct device_attribute *attr, char *buf) 347 { 348 bool val; 349 struct zram *zram = dev_to_zram(dev); 350 351 down_read(&zram->init_lock); 352 spin_lock(&zram->wb_limit_lock); 353 val = zram->wb_limit_enable; 354 spin_unlock(&zram->wb_limit_lock); 355 up_read(&zram->init_lock); 356 357 return scnprintf(buf, PAGE_SIZE, "%d\n", val); 358 } 359 360 static ssize_t writeback_limit_store(struct device *dev, 361 struct device_attribute *attr, const char *buf, size_t len) 362 { 363 struct zram *zram = dev_to_zram(dev); 364 u64 val; 365 ssize_t ret = -EINVAL; 366 367 if (kstrtoull(buf, 10, &val)) 368 return ret; 369 370 down_read(&zram->init_lock); 371 spin_lock(&zram->wb_limit_lock); 372 zram->bd_wb_limit = val; 373 spin_unlock(&zram->wb_limit_lock); 374 up_read(&zram->init_lock); 375 ret = len; 376 377 return ret; 378 } 379 380 static ssize_t writeback_limit_show(struct device *dev, 381 struct device_attribute *attr, char *buf) 382 { 383 u64 val; 384 struct zram *zram = dev_to_zram(dev); 385 386 down_read(&zram->init_lock); 387 spin_lock(&zram->wb_limit_lock); 388 val = zram->bd_wb_limit; 389 spin_unlock(&zram->wb_limit_lock); 390 up_read(&zram->init_lock); 391 392 return scnprintf(buf, PAGE_SIZE, "%llu\n", val); 393 } 394 395 static void reset_bdev(struct zram *zram) 396 { 397 struct block_device *bdev; 398 399 if (!zram->backing_dev) 400 return; 401 402 bdev = zram->bdev; 403 if (zram->old_block_size) 404 set_blocksize(bdev, zram->old_block_size); 405 blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL); 406 /* hope filp_close flush all of IO */ 407 filp_close(zram->backing_dev, NULL); 408 zram->backing_dev = NULL; 409 zram->old_block_size = 0; 410 zram->bdev = NULL; 411 zram->disk->queue->backing_dev_info->capabilities |= 412 BDI_CAP_SYNCHRONOUS_IO; 413 kvfree(zram->bitmap); 414 zram->bitmap = NULL; 415 } 416 417 static ssize_t backing_dev_show(struct device *dev, 418 struct device_attribute *attr, char *buf) 419 { 420 struct file *file; 421 struct zram *zram = dev_to_zram(dev); 422 char *p; 423 ssize_t ret; 424 425 down_read(&zram->init_lock); 426 file = zram->backing_dev; 427 if (!file) { 428 memcpy(buf, "none\n", 5); 429 up_read(&zram->init_lock); 430 return 5; 431 } 432 433 p = file_path(file, buf, PAGE_SIZE - 1); 434 if (IS_ERR(p)) { 435 ret = PTR_ERR(p); 436 goto out; 437 } 438 439 ret = strlen(p); 440 memmove(buf, p, ret); 441 buf[ret++] = '\n'; 442 out: 443 up_read(&zram->init_lock); 444 return ret; 445 } 446 447 static ssize_t backing_dev_store(struct device *dev, 448 struct device_attribute *attr, const char *buf, size_t len) 449 { 450 char *file_name; 451 size_t sz; 452 struct file *backing_dev = NULL; 453 struct inode *inode; 454 struct address_space *mapping; 455 unsigned int bitmap_sz, old_block_size = 0; 456 unsigned long nr_pages, *bitmap = NULL; 457 struct block_device *bdev = NULL; 458 int err; 459 struct zram *zram = dev_to_zram(dev); 460 461 file_name = kmalloc(PATH_MAX, GFP_KERNEL); 462 if (!file_name) 463 return -ENOMEM; 464 465 down_write(&zram->init_lock); 466 if (init_done(zram)) { 467 pr_info("Can't setup backing device for initialized device\n"); 468 err = -EBUSY; 469 goto out; 470 } 471 472 strlcpy(file_name, buf, PATH_MAX); 473 /* ignore trailing newline */ 474 sz = strlen(file_name); 475 if (sz > 0 && file_name[sz - 1] == '\n') 476 file_name[sz - 1] = 0x00; 477 478 backing_dev = filp_open(file_name, O_RDWR|O_LARGEFILE, 0); 479 if (IS_ERR(backing_dev)) { 480 err = PTR_ERR(backing_dev); 481 backing_dev = NULL; 482 goto out; 483 } 484 485 mapping = backing_dev->f_mapping; 486 inode = mapping->host; 487 488 /* Support only block device in this moment */ 489 if (!S_ISBLK(inode->i_mode)) { 490 err = -ENOTBLK; 491 goto out; 492 } 493 494 bdev = bdgrab(I_BDEV(inode)); 495 err = blkdev_get(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL, zram); 496 if (err < 0) { 497 bdev = NULL; 498 goto out; 499 } 500 501 nr_pages = i_size_read(inode) >> PAGE_SHIFT; 502 bitmap_sz = BITS_TO_LONGS(nr_pages) * sizeof(long); 503 bitmap = kvzalloc(bitmap_sz, GFP_KERNEL); 504 if (!bitmap) { 505 err = -ENOMEM; 506 goto out; 507 } 508 509 old_block_size = block_size(bdev); 510 err = set_blocksize(bdev, PAGE_SIZE); 511 if (err) 512 goto out; 513 514 reset_bdev(zram); 515 516 zram->old_block_size = old_block_size; 517 zram->bdev = bdev; 518 zram->backing_dev = backing_dev; 519 zram->bitmap = bitmap; 520 zram->nr_pages = nr_pages; 521 /* 522 * With writeback feature, zram does asynchronous IO so it's no longer 523 * synchronous device so let's remove synchronous io flag. Othewise, 524 * upper layer(e.g., swap) could wait IO completion rather than 525 * (submit and return), which will cause system sluggish. 526 * Furthermore, when the IO function returns(e.g., swap_readpage), 527 * upper layer expects IO was done so it could deallocate the page 528 * freely but in fact, IO is going on so finally could cause 529 * use-after-free when the IO is really done. 530 */ 531 zram->disk->queue->backing_dev_info->capabilities &= 532 ~BDI_CAP_SYNCHRONOUS_IO; 533 up_write(&zram->init_lock); 534 535 pr_info("setup backing device %s\n", file_name); 536 kfree(file_name); 537 538 return len; 539 out: 540 if (bitmap) 541 kvfree(bitmap); 542 543 if (bdev) 544 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); 545 546 if (backing_dev) 547 filp_close(backing_dev, NULL); 548 549 up_write(&zram->init_lock); 550 551 kfree(file_name); 552 553 return err; 554 } 555 556 static unsigned long alloc_block_bdev(struct zram *zram) 557 { 558 unsigned long blk_idx = 1; 559 retry: 560 /* skip 0 bit to confuse zram.handle = 0 */ 561 blk_idx = find_next_zero_bit(zram->bitmap, zram->nr_pages, blk_idx); 562 if (blk_idx == zram->nr_pages) 563 return 0; 564 565 if (test_and_set_bit(blk_idx, zram->bitmap)) 566 goto retry; 567 568 atomic64_inc(&zram->stats.bd_count); 569 return blk_idx; 570 } 571 572 static void free_block_bdev(struct zram *zram, unsigned long blk_idx) 573 { 574 int was_set; 575 576 was_set = test_and_clear_bit(blk_idx, zram->bitmap); 577 WARN_ON_ONCE(!was_set); 578 atomic64_dec(&zram->stats.bd_count); 579 } 580 581 static void zram_page_end_io(struct bio *bio) 582 { 583 struct page *page = bio_first_page_all(bio); 584 585 page_endio(page, op_is_write(bio_op(bio)), 586 blk_status_to_errno(bio->bi_status)); 587 bio_put(bio); 588 } 589 590 /* 591 * Returns 1 if the submission is successful. 592 */ 593 static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec, 594 unsigned long entry, struct bio *parent) 595 { 596 struct bio *bio; 597 598 bio = bio_alloc(GFP_ATOMIC, 1); 599 if (!bio) 600 return -ENOMEM; 601 602 bio->bi_iter.bi_sector = entry * (PAGE_SIZE >> 9); 603 bio_set_dev(bio, zram->bdev); 604 if (!bio_add_page(bio, bvec->bv_page, bvec->bv_len, bvec->bv_offset)) { 605 bio_put(bio); 606 return -EIO; 607 } 608 609 if (!parent) { 610 bio->bi_opf = REQ_OP_READ; 611 bio->bi_end_io = zram_page_end_io; 612 } else { 613 bio->bi_opf = parent->bi_opf; 614 bio_chain(bio, parent); 615 } 616 617 submit_bio(bio); 618 return 1; 619 } 620 621 #define HUGE_WRITEBACK 1 622 #define IDLE_WRITEBACK 2 623 624 static ssize_t writeback_store(struct device *dev, 625 struct device_attribute *attr, const char *buf, size_t len) 626 { 627 struct zram *zram = dev_to_zram(dev); 628 unsigned long nr_pages = zram->disksize >> PAGE_SHIFT; 629 unsigned long index; 630 struct bio bio; 631 struct bio_vec bio_vec; 632 struct page *page; 633 ssize_t ret = len; 634 int mode; 635 unsigned long blk_idx = 0; 636 637 if (sysfs_streq(buf, "idle")) 638 mode = IDLE_WRITEBACK; 639 else if (sysfs_streq(buf, "huge")) 640 mode = HUGE_WRITEBACK; 641 else 642 return -EINVAL; 643 644 down_read(&zram->init_lock); 645 if (!init_done(zram)) { 646 ret = -EINVAL; 647 goto release_init_lock; 648 } 649 650 if (!zram->backing_dev) { 651 ret = -ENODEV; 652 goto release_init_lock; 653 } 654 655 page = alloc_page(GFP_KERNEL); 656 if (!page) { 657 ret = -ENOMEM; 658 goto release_init_lock; 659 } 660 661 for (index = 0; index < nr_pages; index++) { 662 struct bio_vec bvec; 663 664 bvec.bv_page = page; 665 bvec.bv_len = PAGE_SIZE; 666 bvec.bv_offset = 0; 667 668 spin_lock(&zram->wb_limit_lock); 669 if (zram->wb_limit_enable && !zram->bd_wb_limit) { 670 spin_unlock(&zram->wb_limit_lock); 671 ret = -EIO; 672 break; 673 } 674 spin_unlock(&zram->wb_limit_lock); 675 676 if (!blk_idx) { 677 blk_idx = alloc_block_bdev(zram); 678 if (!blk_idx) { 679 ret = -ENOSPC; 680 break; 681 } 682 } 683 684 zram_slot_lock(zram, index); 685 if (!zram_allocated(zram, index)) 686 goto next; 687 688 if (zram_test_flag(zram, index, ZRAM_WB) || 689 zram_test_flag(zram, index, ZRAM_SAME) || 690 zram_test_flag(zram, index, ZRAM_UNDER_WB)) 691 goto next; 692 693 if (mode == IDLE_WRITEBACK && 694 !zram_test_flag(zram, index, ZRAM_IDLE)) 695 goto next; 696 if (mode == HUGE_WRITEBACK && 697 !zram_test_flag(zram, index, ZRAM_HUGE)) 698 goto next; 699 /* 700 * Clearing ZRAM_UNDER_WB is duty of caller. 701 * IOW, zram_free_page never clear it. 702 */ 703 zram_set_flag(zram, index, ZRAM_UNDER_WB); 704 /* Need for hugepage writeback racing */ 705 zram_set_flag(zram, index, ZRAM_IDLE); 706 zram_slot_unlock(zram, index); 707 if (zram_bvec_read(zram, &bvec, index, 0, NULL)) { 708 zram_slot_lock(zram, index); 709 zram_clear_flag(zram, index, ZRAM_UNDER_WB); 710 zram_clear_flag(zram, index, ZRAM_IDLE); 711 zram_slot_unlock(zram, index); 712 continue; 713 } 714 715 bio_init(&bio, &bio_vec, 1); 716 bio_set_dev(&bio, zram->bdev); 717 bio.bi_iter.bi_sector = blk_idx * (PAGE_SIZE >> 9); 718 bio.bi_opf = REQ_OP_WRITE | REQ_SYNC; 719 720 bio_add_page(&bio, bvec.bv_page, bvec.bv_len, 721 bvec.bv_offset); 722 /* 723 * XXX: A single page IO would be inefficient for write 724 * but it would be not bad as starter. 725 */ 726 ret = submit_bio_wait(&bio); 727 if (ret) { 728 zram_slot_lock(zram, index); 729 zram_clear_flag(zram, index, ZRAM_UNDER_WB); 730 zram_clear_flag(zram, index, ZRAM_IDLE); 731 zram_slot_unlock(zram, index); 732 continue; 733 } 734 735 atomic64_inc(&zram->stats.bd_writes); 736 /* 737 * We released zram_slot_lock so need to check if the slot was 738 * changed. If there is freeing for the slot, we can catch it 739 * easily by zram_allocated. 740 * A subtle case is the slot is freed/reallocated/marked as 741 * ZRAM_IDLE again. To close the race, idle_store doesn't 742 * mark ZRAM_IDLE once it found the slot was ZRAM_UNDER_WB. 743 * Thus, we could close the race by checking ZRAM_IDLE bit. 744 */ 745 zram_slot_lock(zram, index); 746 if (!zram_allocated(zram, index) || 747 !zram_test_flag(zram, index, ZRAM_IDLE)) { 748 zram_clear_flag(zram, index, ZRAM_UNDER_WB); 749 zram_clear_flag(zram, index, ZRAM_IDLE); 750 goto next; 751 } 752 753 zram_free_page(zram, index); 754 zram_clear_flag(zram, index, ZRAM_UNDER_WB); 755 zram_set_flag(zram, index, ZRAM_WB); 756 zram_set_element(zram, index, blk_idx); 757 blk_idx = 0; 758 atomic64_inc(&zram->stats.pages_stored); 759 spin_lock(&zram->wb_limit_lock); 760 if (zram->wb_limit_enable && zram->bd_wb_limit > 0) 761 zram->bd_wb_limit -= 1UL << (PAGE_SHIFT - 12); 762 spin_unlock(&zram->wb_limit_lock); 763 next: 764 zram_slot_unlock(zram, index); 765 } 766 767 if (blk_idx) 768 free_block_bdev(zram, blk_idx); 769 __free_page(page); 770 release_init_lock: 771 up_read(&zram->init_lock); 772 773 return ret; 774 } 775 776 struct zram_work { 777 struct work_struct work; 778 struct zram *zram; 779 unsigned long entry; 780 struct bio *bio; 781 struct bio_vec bvec; 782 }; 783 784 #if PAGE_SIZE != 4096 785 static void zram_sync_read(struct work_struct *work) 786 { 787 struct zram_work *zw = container_of(work, struct zram_work, work); 788 struct zram *zram = zw->zram; 789 unsigned long entry = zw->entry; 790 struct bio *bio = zw->bio; 791 792 read_from_bdev_async(zram, &zw->bvec, entry, bio); 793 } 794 795 /* 796 * Block layer want one ->make_request_fn to be active at a time 797 * so if we use chained IO with parent IO in same context, 798 * it's a deadlock. To avoid, it, it uses worker thread context. 799 */ 800 static int read_from_bdev_sync(struct zram *zram, struct bio_vec *bvec, 801 unsigned long entry, struct bio *bio) 802 { 803 struct zram_work work; 804 805 work.bvec = *bvec; 806 work.zram = zram; 807 work.entry = entry; 808 work.bio = bio; 809 810 INIT_WORK_ONSTACK(&work.work, zram_sync_read); 811 queue_work(system_unbound_wq, &work.work); 812 flush_work(&work.work); 813 destroy_work_on_stack(&work.work); 814 815 return 1; 816 } 817 #else 818 static int read_from_bdev_sync(struct zram *zram, struct bio_vec *bvec, 819 unsigned long entry, struct bio *bio) 820 { 821 WARN_ON(1); 822 return -EIO; 823 } 824 #endif 825 826 static int read_from_bdev(struct zram *zram, struct bio_vec *bvec, 827 unsigned long entry, struct bio *parent, bool sync) 828 { 829 atomic64_inc(&zram->stats.bd_reads); 830 if (sync) 831 return read_from_bdev_sync(zram, bvec, entry, parent); 832 else 833 return read_from_bdev_async(zram, bvec, entry, parent); 834 } 835 #else 836 static inline void reset_bdev(struct zram *zram) {}; 837 static int read_from_bdev(struct zram *zram, struct bio_vec *bvec, 838 unsigned long entry, struct bio *parent, bool sync) 839 { 840 return -EIO; 841 } 842 843 static void free_block_bdev(struct zram *zram, unsigned long blk_idx) {}; 844 #endif 845 846 #ifdef CONFIG_ZRAM_MEMORY_TRACKING 847 848 static struct dentry *zram_debugfs_root; 849 850 static void zram_debugfs_create(void) 851 { 852 zram_debugfs_root = debugfs_create_dir("zram", NULL); 853 } 854 855 static void zram_debugfs_destroy(void) 856 { 857 debugfs_remove_recursive(zram_debugfs_root); 858 } 859 860 static void zram_accessed(struct zram *zram, u32 index) 861 { 862 zram_clear_flag(zram, index, ZRAM_IDLE); 863 zram->table[index].ac_time = ktime_get_boottime(); 864 } 865 866 static ssize_t read_block_state(struct file *file, char __user *buf, 867 size_t count, loff_t *ppos) 868 { 869 char *kbuf; 870 ssize_t index, written = 0; 871 struct zram *zram = file->private_data; 872 unsigned long nr_pages = zram->disksize >> PAGE_SHIFT; 873 struct timespec64 ts; 874 875 kbuf = kvmalloc(count, GFP_KERNEL); 876 if (!kbuf) 877 return -ENOMEM; 878 879 down_read(&zram->init_lock); 880 if (!init_done(zram)) { 881 up_read(&zram->init_lock); 882 kvfree(kbuf); 883 return -EINVAL; 884 } 885 886 for (index = *ppos; index < nr_pages; index++) { 887 int copied; 888 889 zram_slot_lock(zram, index); 890 if (!zram_allocated(zram, index)) 891 goto next; 892 893 ts = ktime_to_timespec64(zram->table[index].ac_time); 894 copied = snprintf(kbuf + written, count, 895 "%12zd %12lld.%06lu %c%c%c%c\n", 896 index, (s64)ts.tv_sec, 897 ts.tv_nsec / NSEC_PER_USEC, 898 zram_test_flag(zram, index, ZRAM_SAME) ? 's' : '.', 899 zram_test_flag(zram, index, ZRAM_WB) ? 'w' : '.', 900 zram_test_flag(zram, index, ZRAM_HUGE) ? 'h' : '.', 901 zram_test_flag(zram, index, ZRAM_IDLE) ? 'i' : '.'); 902 903 if (count < copied) { 904 zram_slot_unlock(zram, index); 905 break; 906 } 907 written += copied; 908 count -= copied; 909 next: 910 zram_slot_unlock(zram, index); 911 *ppos += 1; 912 } 913 914 up_read(&zram->init_lock); 915 if (copy_to_user(buf, kbuf, written)) 916 written = -EFAULT; 917 kvfree(kbuf); 918 919 return written; 920 } 921 922 static const struct file_operations proc_zram_block_state_op = { 923 .open = simple_open, 924 .read = read_block_state, 925 .llseek = default_llseek, 926 }; 927 928 static void zram_debugfs_register(struct zram *zram) 929 { 930 if (!zram_debugfs_root) 931 return; 932 933 zram->debugfs_dir = debugfs_create_dir(zram->disk->disk_name, 934 zram_debugfs_root); 935 debugfs_create_file("block_state", 0400, zram->debugfs_dir, 936 zram, &proc_zram_block_state_op); 937 } 938 939 static void zram_debugfs_unregister(struct zram *zram) 940 { 941 debugfs_remove_recursive(zram->debugfs_dir); 942 } 943 #else 944 static void zram_debugfs_create(void) {}; 945 static void zram_debugfs_destroy(void) {}; 946 static void zram_accessed(struct zram *zram, u32 index) 947 { 948 zram_clear_flag(zram, index, ZRAM_IDLE); 949 }; 950 static void zram_debugfs_register(struct zram *zram) {}; 951 static void zram_debugfs_unregister(struct zram *zram) {}; 952 #endif 953 954 /* 955 * We switched to per-cpu streams and this attr is not needed anymore. 956 * However, we will keep it around for some time, because: 957 * a) we may revert per-cpu streams in the future 958 * b) it's visible to user space and we need to follow our 2 years 959 * retirement rule; but we already have a number of 'soon to be 960 * altered' attrs, so max_comp_streams need to wait for the next 961 * layoff cycle. 962 */ 963 static ssize_t max_comp_streams_show(struct device *dev, 964 struct device_attribute *attr, char *buf) 965 { 966 return scnprintf(buf, PAGE_SIZE, "%d\n", num_online_cpus()); 967 } 968 969 static ssize_t max_comp_streams_store(struct device *dev, 970 struct device_attribute *attr, const char *buf, size_t len) 971 { 972 return len; 973 } 974 975 static ssize_t comp_algorithm_show(struct device *dev, 976 struct device_attribute *attr, char *buf) 977 { 978 size_t sz; 979 struct zram *zram = dev_to_zram(dev); 980 981 down_read(&zram->init_lock); 982 sz = zcomp_available_show(zram->compressor, buf); 983 up_read(&zram->init_lock); 984 985 return sz; 986 } 987 988 static ssize_t comp_algorithm_store(struct device *dev, 989 struct device_attribute *attr, const char *buf, size_t len) 990 { 991 struct zram *zram = dev_to_zram(dev); 992 char compressor[ARRAY_SIZE(zram->compressor)]; 993 size_t sz; 994 995 strlcpy(compressor, buf, sizeof(compressor)); 996 /* ignore trailing newline */ 997 sz = strlen(compressor); 998 if (sz > 0 && compressor[sz - 1] == '\n') 999 compressor[sz - 1] = 0x00; 1000 1001 if (!zcomp_available_algorithm(compressor)) 1002 return -EINVAL; 1003 1004 down_write(&zram->init_lock); 1005 if (init_done(zram)) { 1006 up_write(&zram->init_lock); 1007 pr_info("Can't change algorithm for initialized device\n"); 1008 return -EBUSY; 1009 } 1010 1011 strcpy(zram->compressor, compressor); 1012 up_write(&zram->init_lock); 1013 return len; 1014 } 1015 1016 static ssize_t compact_store(struct device *dev, 1017 struct device_attribute *attr, const char *buf, size_t len) 1018 { 1019 struct zram *zram = dev_to_zram(dev); 1020 1021 down_read(&zram->init_lock); 1022 if (!init_done(zram)) { 1023 up_read(&zram->init_lock); 1024 return -EINVAL; 1025 } 1026 1027 zs_compact(zram->mem_pool); 1028 up_read(&zram->init_lock); 1029 1030 return len; 1031 } 1032 1033 static ssize_t io_stat_show(struct device *dev, 1034 struct device_attribute *attr, char *buf) 1035 { 1036 struct zram *zram = dev_to_zram(dev); 1037 ssize_t ret; 1038 1039 down_read(&zram->init_lock); 1040 ret = scnprintf(buf, PAGE_SIZE, 1041 "%8llu %8llu %8llu %8llu\n", 1042 (u64)atomic64_read(&zram->stats.failed_reads), 1043 (u64)atomic64_read(&zram->stats.failed_writes), 1044 (u64)atomic64_read(&zram->stats.invalid_io), 1045 (u64)atomic64_read(&zram->stats.notify_free)); 1046 up_read(&zram->init_lock); 1047 1048 return ret; 1049 } 1050 1051 static ssize_t mm_stat_show(struct device *dev, 1052 struct device_attribute *attr, char *buf) 1053 { 1054 struct zram *zram = dev_to_zram(dev); 1055 struct zs_pool_stats pool_stats; 1056 u64 orig_size, mem_used = 0; 1057 long max_used; 1058 ssize_t ret; 1059 1060 memset(&pool_stats, 0x00, sizeof(struct zs_pool_stats)); 1061 1062 down_read(&zram->init_lock); 1063 if (init_done(zram)) { 1064 mem_used = zs_get_total_pages(zram->mem_pool); 1065 zs_pool_stats(zram->mem_pool, &pool_stats); 1066 } 1067 1068 orig_size = atomic64_read(&zram->stats.pages_stored); 1069 max_used = atomic_long_read(&zram->stats.max_used_pages); 1070 1071 ret = scnprintf(buf, PAGE_SIZE, 1072 "%8llu %8llu %8llu %8lu %8ld %8llu %8lu %8llu\n", 1073 orig_size << PAGE_SHIFT, 1074 (u64)atomic64_read(&zram->stats.compr_data_size), 1075 mem_used << PAGE_SHIFT, 1076 zram->limit_pages << PAGE_SHIFT, 1077 max_used << PAGE_SHIFT, 1078 (u64)atomic64_read(&zram->stats.same_pages), 1079 pool_stats.pages_compacted, 1080 (u64)atomic64_read(&zram->stats.huge_pages)); 1081 up_read(&zram->init_lock); 1082 1083 return ret; 1084 } 1085 1086 #ifdef CONFIG_ZRAM_WRITEBACK 1087 #define FOUR_K(x) ((x) * (1 << (PAGE_SHIFT - 12))) 1088 static ssize_t bd_stat_show(struct device *dev, 1089 struct device_attribute *attr, char *buf) 1090 { 1091 struct zram *zram = dev_to_zram(dev); 1092 ssize_t ret; 1093 1094 down_read(&zram->init_lock); 1095 ret = scnprintf(buf, PAGE_SIZE, 1096 "%8llu %8llu %8llu\n", 1097 FOUR_K((u64)atomic64_read(&zram->stats.bd_count)), 1098 FOUR_K((u64)atomic64_read(&zram->stats.bd_reads)), 1099 FOUR_K((u64)atomic64_read(&zram->stats.bd_writes))); 1100 up_read(&zram->init_lock); 1101 1102 return ret; 1103 } 1104 #endif 1105 1106 static ssize_t debug_stat_show(struct device *dev, 1107 struct device_attribute *attr, char *buf) 1108 { 1109 int version = 1; 1110 struct zram *zram = dev_to_zram(dev); 1111 ssize_t ret; 1112 1113 down_read(&zram->init_lock); 1114 ret = scnprintf(buf, PAGE_SIZE, 1115 "version: %d\n%8llu %8llu\n", 1116 version, 1117 (u64)atomic64_read(&zram->stats.writestall), 1118 (u64)atomic64_read(&zram->stats.miss_free)); 1119 up_read(&zram->init_lock); 1120 1121 return ret; 1122 } 1123 1124 static DEVICE_ATTR_RO(io_stat); 1125 static DEVICE_ATTR_RO(mm_stat); 1126 #ifdef CONFIG_ZRAM_WRITEBACK 1127 static DEVICE_ATTR_RO(bd_stat); 1128 #endif 1129 static DEVICE_ATTR_RO(debug_stat); 1130 1131 static void zram_meta_free(struct zram *zram, u64 disksize) 1132 { 1133 size_t num_pages = disksize >> PAGE_SHIFT; 1134 size_t index; 1135 1136 /* Free all pages that are still in this zram device */ 1137 for (index = 0; index < num_pages; index++) 1138 zram_free_page(zram, index); 1139 1140 zs_destroy_pool(zram->mem_pool); 1141 vfree(zram->table); 1142 } 1143 1144 static bool zram_meta_alloc(struct zram *zram, u64 disksize) 1145 { 1146 size_t num_pages; 1147 1148 num_pages = disksize >> PAGE_SHIFT; 1149 zram->table = vzalloc(array_size(num_pages, sizeof(*zram->table))); 1150 if (!zram->table) 1151 return false; 1152 1153 zram->mem_pool = zs_create_pool(zram->disk->disk_name); 1154 if (!zram->mem_pool) { 1155 vfree(zram->table); 1156 return false; 1157 } 1158 1159 if (!huge_class_size) 1160 huge_class_size = zs_huge_class_size(zram->mem_pool); 1161 return true; 1162 } 1163 1164 /* 1165 * To protect concurrent access to the same index entry, 1166 * caller should hold this table index entry's bit_spinlock to 1167 * indicate this index entry is accessing. 1168 */ 1169 static void zram_free_page(struct zram *zram, size_t index) 1170 { 1171 unsigned long handle; 1172 1173 #ifdef CONFIG_ZRAM_MEMORY_TRACKING 1174 zram->table[index].ac_time = 0; 1175 #endif 1176 if (zram_test_flag(zram, index, ZRAM_IDLE)) 1177 zram_clear_flag(zram, index, ZRAM_IDLE); 1178 1179 if (zram_test_flag(zram, index, ZRAM_HUGE)) { 1180 zram_clear_flag(zram, index, ZRAM_HUGE); 1181 atomic64_dec(&zram->stats.huge_pages); 1182 } 1183 1184 if (zram_test_flag(zram, index, ZRAM_WB)) { 1185 zram_clear_flag(zram, index, ZRAM_WB); 1186 free_block_bdev(zram, zram_get_element(zram, index)); 1187 goto out; 1188 } 1189 1190 /* 1191 * No memory is allocated for same element filled pages. 1192 * Simply clear same page flag. 1193 */ 1194 if (zram_test_flag(zram, index, ZRAM_SAME)) { 1195 zram_clear_flag(zram, index, ZRAM_SAME); 1196 atomic64_dec(&zram->stats.same_pages); 1197 goto out; 1198 } 1199 1200 handle = zram_get_handle(zram, index); 1201 if (!handle) 1202 return; 1203 1204 zs_free(zram->mem_pool, handle); 1205 1206 atomic64_sub(zram_get_obj_size(zram, index), 1207 &zram->stats.compr_data_size); 1208 out: 1209 atomic64_dec(&zram->stats.pages_stored); 1210 zram_set_handle(zram, index, 0); 1211 zram_set_obj_size(zram, index, 0); 1212 WARN_ON_ONCE(zram->table[index].flags & 1213 ~(1UL << ZRAM_LOCK | 1UL << ZRAM_UNDER_WB)); 1214 } 1215 1216 static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index, 1217 struct bio *bio, bool partial_io) 1218 { 1219 int ret; 1220 unsigned long handle; 1221 unsigned int size; 1222 void *src, *dst; 1223 1224 zram_slot_lock(zram, index); 1225 if (zram_test_flag(zram, index, ZRAM_WB)) { 1226 struct bio_vec bvec; 1227 1228 zram_slot_unlock(zram, index); 1229 1230 bvec.bv_page = page; 1231 bvec.bv_len = PAGE_SIZE; 1232 bvec.bv_offset = 0; 1233 return read_from_bdev(zram, &bvec, 1234 zram_get_element(zram, index), 1235 bio, partial_io); 1236 } 1237 1238 handle = zram_get_handle(zram, index); 1239 if (!handle || zram_test_flag(zram, index, ZRAM_SAME)) { 1240 unsigned long value; 1241 void *mem; 1242 1243 value = handle ? zram_get_element(zram, index) : 0; 1244 mem = kmap_atomic(page); 1245 zram_fill_page(mem, PAGE_SIZE, value); 1246 kunmap_atomic(mem); 1247 zram_slot_unlock(zram, index); 1248 return 0; 1249 } 1250 1251 size = zram_get_obj_size(zram, index); 1252 1253 src = zs_map_object(zram->mem_pool, handle, ZS_MM_RO); 1254 if (size == PAGE_SIZE) { 1255 dst = kmap_atomic(page); 1256 memcpy(dst, src, PAGE_SIZE); 1257 kunmap_atomic(dst); 1258 ret = 0; 1259 } else { 1260 struct zcomp_strm *zstrm = zcomp_stream_get(zram->comp); 1261 1262 dst = kmap_atomic(page); 1263 ret = zcomp_decompress(zstrm, src, size, dst); 1264 kunmap_atomic(dst); 1265 zcomp_stream_put(zram->comp); 1266 } 1267 zs_unmap_object(zram->mem_pool, handle); 1268 zram_slot_unlock(zram, index); 1269 1270 /* Should NEVER happen. Return bio error if it does. */ 1271 if (unlikely(ret)) 1272 pr_err("Decompression failed! err=%d, page=%u\n", ret, index); 1273 1274 return ret; 1275 } 1276 1277 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, 1278 u32 index, int offset, struct bio *bio) 1279 { 1280 int ret; 1281 struct page *page; 1282 1283 page = bvec->bv_page; 1284 if (is_partial_io(bvec)) { 1285 /* Use a temporary buffer to decompress the page */ 1286 page = alloc_page(GFP_NOIO|__GFP_HIGHMEM); 1287 if (!page) 1288 return -ENOMEM; 1289 } 1290 1291 ret = __zram_bvec_read(zram, page, index, bio, is_partial_io(bvec)); 1292 if (unlikely(ret)) 1293 goto out; 1294 1295 if (is_partial_io(bvec)) { 1296 void *dst = kmap_atomic(bvec->bv_page); 1297 void *src = kmap_atomic(page); 1298 1299 memcpy(dst + bvec->bv_offset, src + offset, bvec->bv_len); 1300 kunmap_atomic(src); 1301 kunmap_atomic(dst); 1302 } 1303 out: 1304 if (is_partial_io(bvec)) 1305 __free_page(page); 1306 1307 return ret; 1308 } 1309 1310 static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, 1311 u32 index, struct bio *bio) 1312 { 1313 int ret = 0; 1314 unsigned long alloced_pages; 1315 unsigned long handle = 0; 1316 unsigned int comp_len = 0; 1317 void *src, *dst, *mem; 1318 struct zcomp_strm *zstrm; 1319 struct page *page = bvec->bv_page; 1320 unsigned long element = 0; 1321 enum zram_pageflags flags = 0; 1322 1323 mem = kmap_atomic(page); 1324 if (page_same_filled(mem, &element)) { 1325 kunmap_atomic(mem); 1326 /* Free memory associated with this sector now. */ 1327 flags = ZRAM_SAME; 1328 atomic64_inc(&zram->stats.same_pages); 1329 goto out; 1330 } 1331 kunmap_atomic(mem); 1332 1333 compress_again: 1334 zstrm = zcomp_stream_get(zram->comp); 1335 src = kmap_atomic(page); 1336 ret = zcomp_compress(zstrm, src, &comp_len); 1337 kunmap_atomic(src); 1338 1339 if (unlikely(ret)) { 1340 zcomp_stream_put(zram->comp); 1341 pr_err("Compression failed! err=%d\n", ret); 1342 zs_free(zram->mem_pool, handle); 1343 return ret; 1344 } 1345 1346 if (comp_len >= huge_class_size) 1347 comp_len = PAGE_SIZE; 1348 /* 1349 * handle allocation has 2 paths: 1350 * a) fast path is executed with preemption disabled (for 1351 * per-cpu streams) and has __GFP_DIRECT_RECLAIM bit clear, 1352 * since we can't sleep; 1353 * b) slow path enables preemption and attempts to allocate 1354 * the page with __GFP_DIRECT_RECLAIM bit set. we have to 1355 * put per-cpu compression stream and, thus, to re-do 1356 * the compression once handle is allocated. 1357 * 1358 * if we have a 'non-null' handle here then we are coming 1359 * from the slow path and handle has already been allocated. 1360 */ 1361 if (!handle) 1362 handle = zs_malloc(zram->mem_pool, comp_len, 1363 __GFP_KSWAPD_RECLAIM | 1364 __GFP_NOWARN | 1365 __GFP_HIGHMEM | 1366 __GFP_MOVABLE); 1367 if (!handle) { 1368 zcomp_stream_put(zram->comp); 1369 atomic64_inc(&zram->stats.writestall); 1370 handle = zs_malloc(zram->mem_pool, comp_len, 1371 GFP_NOIO | __GFP_HIGHMEM | 1372 __GFP_MOVABLE); 1373 if (handle) 1374 goto compress_again; 1375 return -ENOMEM; 1376 } 1377 1378 alloced_pages = zs_get_total_pages(zram->mem_pool); 1379 update_used_max(zram, alloced_pages); 1380 1381 if (zram->limit_pages && alloced_pages > zram->limit_pages) { 1382 zcomp_stream_put(zram->comp); 1383 zs_free(zram->mem_pool, handle); 1384 return -ENOMEM; 1385 } 1386 1387 dst = zs_map_object(zram->mem_pool, handle, ZS_MM_WO); 1388 1389 src = zstrm->buffer; 1390 if (comp_len == PAGE_SIZE) 1391 src = kmap_atomic(page); 1392 memcpy(dst, src, comp_len); 1393 if (comp_len == PAGE_SIZE) 1394 kunmap_atomic(src); 1395 1396 zcomp_stream_put(zram->comp); 1397 zs_unmap_object(zram->mem_pool, handle); 1398 atomic64_add(comp_len, &zram->stats.compr_data_size); 1399 out: 1400 /* 1401 * Free memory associated with this sector 1402 * before overwriting unused sectors. 1403 */ 1404 zram_slot_lock(zram, index); 1405 zram_free_page(zram, index); 1406 1407 if (comp_len == PAGE_SIZE) { 1408 zram_set_flag(zram, index, ZRAM_HUGE); 1409 atomic64_inc(&zram->stats.huge_pages); 1410 } 1411 1412 if (flags) { 1413 zram_set_flag(zram, index, flags); 1414 zram_set_element(zram, index, element); 1415 } else { 1416 zram_set_handle(zram, index, handle); 1417 zram_set_obj_size(zram, index, comp_len); 1418 } 1419 zram_slot_unlock(zram, index); 1420 1421 /* Update stats */ 1422 atomic64_inc(&zram->stats.pages_stored); 1423 return ret; 1424 } 1425 1426 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, 1427 u32 index, int offset, struct bio *bio) 1428 { 1429 int ret; 1430 struct page *page = NULL; 1431 void *src; 1432 struct bio_vec vec; 1433 1434 vec = *bvec; 1435 if (is_partial_io(bvec)) { 1436 void *dst; 1437 /* 1438 * This is a partial IO. We need to read the full page 1439 * before to write the changes. 1440 */ 1441 page = alloc_page(GFP_NOIO|__GFP_HIGHMEM); 1442 if (!page) 1443 return -ENOMEM; 1444 1445 ret = __zram_bvec_read(zram, page, index, bio, true); 1446 if (ret) 1447 goto out; 1448 1449 src = kmap_atomic(bvec->bv_page); 1450 dst = kmap_atomic(page); 1451 memcpy(dst + offset, src + bvec->bv_offset, bvec->bv_len); 1452 kunmap_atomic(dst); 1453 kunmap_atomic(src); 1454 1455 vec.bv_page = page; 1456 vec.bv_len = PAGE_SIZE; 1457 vec.bv_offset = 0; 1458 } 1459 1460 ret = __zram_bvec_write(zram, &vec, index, bio); 1461 out: 1462 if (is_partial_io(bvec)) 1463 __free_page(page); 1464 return ret; 1465 } 1466 1467 /* 1468 * zram_bio_discard - handler on discard request 1469 * @index: physical block index in PAGE_SIZE units 1470 * @offset: byte offset within physical block 1471 */ 1472 static void zram_bio_discard(struct zram *zram, u32 index, 1473 int offset, struct bio *bio) 1474 { 1475 size_t n = bio->bi_iter.bi_size; 1476 1477 /* 1478 * zram manages data in physical block size units. Because logical block 1479 * size isn't identical with physical block size on some arch, we 1480 * could get a discard request pointing to a specific offset within a 1481 * certain physical block. Although we can handle this request by 1482 * reading that physiclal block and decompressing and partially zeroing 1483 * and re-compressing and then re-storing it, this isn't reasonable 1484 * because our intent with a discard request is to save memory. So 1485 * skipping this logical block is appropriate here. 1486 */ 1487 if (offset) { 1488 if (n <= (PAGE_SIZE - offset)) 1489 return; 1490 1491 n -= (PAGE_SIZE - offset); 1492 index++; 1493 } 1494 1495 while (n >= PAGE_SIZE) { 1496 zram_slot_lock(zram, index); 1497 zram_free_page(zram, index); 1498 zram_slot_unlock(zram, index); 1499 atomic64_inc(&zram->stats.notify_free); 1500 index++; 1501 n -= PAGE_SIZE; 1502 } 1503 } 1504 1505 /* 1506 * Returns errno if it has some problem. Otherwise return 0 or 1. 1507 * Returns 0 if IO request was done synchronously 1508 * Returns 1 if IO request was successfully submitted. 1509 */ 1510 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index, 1511 int offset, unsigned int op, struct bio *bio) 1512 { 1513 unsigned long start_time = jiffies; 1514 struct request_queue *q = zram->disk->queue; 1515 int ret; 1516 1517 generic_start_io_acct(q, op, bvec->bv_len >> SECTOR_SHIFT, 1518 &zram->disk->part0); 1519 1520 if (!op_is_write(op)) { 1521 atomic64_inc(&zram->stats.num_reads); 1522 ret = zram_bvec_read(zram, bvec, index, offset, bio); 1523 flush_dcache_page(bvec->bv_page); 1524 } else { 1525 atomic64_inc(&zram->stats.num_writes); 1526 ret = zram_bvec_write(zram, bvec, index, offset, bio); 1527 } 1528 1529 generic_end_io_acct(q, op, &zram->disk->part0, start_time); 1530 1531 zram_slot_lock(zram, index); 1532 zram_accessed(zram, index); 1533 zram_slot_unlock(zram, index); 1534 1535 if (unlikely(ret < 0)) { 1536 if (!op_is_write(op)) 1537 atomic64_inc(&zram->stats.failed_reads); 1538 else 1539 atomic64_inc(&zram->stats.failed_writes); 1540 } 1541 1542 return ret; 1543 } 1544 1545 static void __zram_make_request(struct zram *zram, struct bio *bio) 1546 { 1547 int offset; 1548 u32 index; 1549 struct bio_vec bvec; 1550 struct bvec_iter iter; 1551 1552 index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT; 1553 offset = (bio->bi_iter.bi_sector & 1554 (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT; 1555 1556 switch (bio_op(bio)) { 1557 case REQ_OP_DISCARD: 1558 case REQ_OP_WRITE_ZEROES: 1559 zram_bio_discard(zram, index, offset, bio); 1560 bio_endio(bio); 1561 return; 1562 default: 1563 break; 1564 } 1565 1566 bio_for_each_segment(bvec, bio, iter) { 1567 struct bio_vec bv = bvec; 1568 unsigned int unwritten = bvec.bv_len; 1569 1570 do { 1571 bv.bv_len = min_t(unsigned int, PAGE_SIZE - offset, 1572 unwritten); 1573 if (zram_bvec_rw(zram, &bv, index, offset, 1574 bio_op(bio), bio) < 0) 1575 goto out; 1576 1577 bv.bv_offset += bv.bv_len; 1578 unwritten -= bv.bv_len; 1579 1580 update_position(&index, &offset, &bv); 1581 } while (unwritten); 1582 } 1583 1584 bio_endio(bio); 1585 return; 1586 1587 out: 1588 bio_io_error(bio); 1589 } 1590 1591 /* 1592 * Handler function for all zram I/O requests. 1593 */ 1594 static blk_qc_t zram_make_request(struct request_queue *queue, struct bio *bio) 1595 { 1596 struct zram *zram = queue->queuedata; 1597 1598 if (!valid_io_request(zram, bio->bi_iter.bi_sector, 1599 bio->bi_iter.bi_size)) { 1600 atomic64_inc(&zram->stats.invalid_io); 1601 goto error; 1602 } 1603 1604 __zram_make_request(zram, bio); 1605 return BLK_QC_T_NONE; 1606 1607 error: 1608 bio_io_error(bio); 1609 return BLK_QC_T_NONE; 1610 } 1611 1612 static void zram_slot_free_notify(struct block_device *bdev, 1613 unsigned long index) 1614 { 1615 struct zram *zram; 1616 1617 zram = bdev->bd_disk->private_data; 1618 1619 atomic64_inc(&zram->stats.notify_free); 1620 if (!zram_slot_trylock(zram, index)) { 1621 atomic64_inc(&zram->stats.miss_free); 1622 return; 1623 } 1624 1625 zram_free_page(zram, index); 1626 zram_slot_unlock(zram, index); 1627 } 1628 1629 static int zram_rw_page(struct block_device *bdev, sector_t sector, 1630 struct page *page, unsigned int op) 1631 { 1632 int offset, ret; 1633 u32 index; 1634 struct zram *zram; 1635 struct bio_vec bv; 1636 1637 if (PageTransHuge(page)) 1638 return -ENOTSUPP; 1639 zram = bdev->bd_disk->private_data; 1640 1641 if (!valid_io_request(zram, sector, PAGE_SIZE)) { 1642 atomic64_inc(&zram->stats.invalid_io); 1643 ret = -EINVAL; 1644 goto out; 1645 } 1646 1647 index = sector >> SECTORS_PER_PAGE_SHIFT; 1648 offset = (sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT; 1649 1650 bv.bv_page = page; 1651 bv.bv_len = PAGE_SIZE; 1652 bv.bv_offset = 0; 1653 1654 ret = zram_bvec_rw(zram, &bv, index, offset, op, NULL); 1655 out: 1656 /* 1657 * If I/O fails, just return error(ie, non-zero) without 1658 * calling page_endio. 1659 * It causes resubmit the I/O with bio request by upper functions 1660 * of rw_page(e.g., swap_readpage, __swap_writepage) and 1661 * bio->bi_end_io does things to handle the error 1662 * (e.g., SetPageError, set_page_dirty and extra works). 1663 */ 1664 if (unlikely(ret < 0)) 1665 return ret; 1666 1667 switch (ret) { 1668 case 0: 1669 page_endio(page, op_is_write(op), 0); 1670 break; 1671 case 1: 1672 ret = 0; 1673 break; 1674 default: 1675 WARN_ON(1); 1676 } 1677 return ret; 1678 } 1679 1680 static void zram_reset_device(struct zram *zram) 1681 { 1682 struct zcomp *comp; 1683 u64 disksize; 1684 1685 down_write(&zram->init_lock); 1686 1687 zram->limit_pages = 0; 1688 1689 if (!init_done(zram)) { 1690 up_write(&zram->init_lock); 1691 return; 1692 } 1693 1694 comp = zram->comp; 1695 disksize = zram->disksize; 1696 zram->disksize = 0; 1697 1698 set_capacity(zram->disk, 0); 1699 part_stat_set_all(&zram->disk->part0, 0); 1700 1701 up_write(&zram->init_lock); 1702 /* I/O operation under all of CPU are done so let's free */ 1703 zram_meta_free(zram, disksize); 1704 memset(&zram->stats, 0, sizeof(zram->stats)); 1705 zcomp_destroy(comp); 1706 reset_bdev(zram); 1707 } 1708 1709 static ssize_t disksize_store(struct device *dev, 1710 struct device_attribute *attr, const char *buf, size_t len) 1711 { 1712 u64 disksize; 1713 struct zcomp *comp; 1714 struct zram *zram = dev_to_zram(dev); 1715 int err; 1716 1717 disksize = memparse(buf, NULL); 1718 if (!disksize) 1719 return -EINVAL; 1720 1721 down_write(&zram->init_lock); 1722 if (init_done(zram)) { 1723 pr_info("Cannot change disksize for initialized device\n"); 1724 err = -EBUSY; 1725 goto out_unlock; 1726 } 1727 1728 disksize = PAGE_ALIGN(disksize); 1729 if (!zram_meta_alloc(zram, disksize)) { 1730 err = -ENOMEM; 1731 goto out_unlock; 1732 } 1733 1734 comp = zcomp_create(zram->compressor); 1735 if (IS_ERR(comp)) { 1736 pr_err("Cannot initialise %s compressing backend\n", 1737 zram->compressor); 1738 err = PTR_ERR(comp); 1739 goto out_free_meta; 1740 } 1741 1742 zram->comp = comp; 1743 zram->disksize = disksize; 1744 set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT); 1745 1746 revalidate_disk(zram->disk); 1747 up_write(&zram->init_lock); 1748 1749 return len; 1750 1751 out_free_meta: 1752 zram_meta_free(zram, disksize); 1753 out_unlock: 1754 up_write(&zram->init_lock); 1755 return err; 1756 } 1757 1758 static ssize_t reset_store(struct device *dev, 1759 struct device_attribute *attr, const char *buf, size_t len) 1760 { 1761 int ret; 1762 unsigned short do_reset; 1763 struct zram *zram; 1764 struct block_device *bdev; 1765 1766 ret = kstrtou16(buf, 10, &do_reset); 1767 if (ret) 1768 return ret; 1769 1770 if (!do_reset) 1771 return -EINVAL; 1772 1773 zram = dev_to_zram(dev); 1774 bdev = bdget_disk(zram->disk, 0); 1775 if (!bdev) 1776 return -ENOMEM; 1777 1778 mutex_lock(&bdev->bd_mutex); 1779 /* Do not reset an active device or claimed device */ 1780 if (bdev->bd_openers || zram->claim) { 1781 mutex_unlock(&bdev->bd_mutex); 1782 bdput(bdev); 1783 return -EBUSY; 1784 } 1785 1786 /* From now on, anyone can't open /dev/zram[0-9] */ 1787 zram->claim = true; 1788 mutex_unlock(&bdev->bd_mutex); 1789 1790 /* Make sure all the pending I/O are finished */ 1791 fsync_bdev(bdev); 1792 zram_reset_device(zram); 1793 revalidate_disk(zram->disk); 1794 bdput(bdev); 1795 1796 mutex_lock(&bdev->bd_mutex); 1797 zram->claim = false; 1798 mutex_unlock(&bdev->bd_mutex); 1799 1800 return len; 1801 } 1802 1803 static int zram_open(struct block_device *bdev, fmode_t mode) 1804 { 1805 int ret = 0; 1806 struct zram *zram; 1807 1808 WARN_ON(!mutex_is_locked(&bdev->bd_mutex)); 1809 1810 zram = bdev->bd_disk->private_data; 1811 /* zram was claimed to reset so open request fails */ 1812 if (zram->claim) 1813 ret = -EBUSY; 1814 1815 return ret; 1816 } 1817 1818 static const struct block_device_operations zram_devops = { 1819 .open = zram_open, 1820 .swap_slot_free_notify = zram_slot_free_notify, 1821 .rw_page = zram_rw_page, 1822 .owner = THIS_MODULE 1823 }; 1824 1825 static DEVICE_ATTR_WO(compact); 1826 static DEVICE_ATTR_RW(disksize); 1827 static DEVICE_ATTR_RO(initstate); 1828 static DEVICE_ATTR_WO(reset); 1829 static DEVICE_ATTR_WO(mem_limit); 1830 static DEVICE_ATTR_WO(mem_used_max); 1831 static DEVICE_ATTR_WO(idle); 1832 static DEVICE_ATTR_RW(max_comp_streams); 1833 static DEVICE_ATTR_RW(comp_algorithm); 1834 #ifdef CONFIG_ZRAM_WRITEBACK 1835 static DEVICE_ATTR_RW(backing_dev); 1836 static DEVICE_ATTR_WO(writeback); 1837 static DEVICE_ATTR_RW(writeback_limit); 1838 static DEVICE_ATTR_RW(writeback_limit_enable); 1839 #endif 1840 1841 static struct attribute *zram_disk_attrs[] = { 1842 &dev_attr_disksize.attr, 1843 &dev_attr_initstate.attr, 1844 &dev_attr_reset.attr, 1845 &dev_attr_compact.attr, 1846 &dev_attr_mem_limit.attr, 1847 &dev_attr_mem_used_max.attr, 1848 &dev_attr_idle.attr, 1849 &dev_attr_max_comp_streams.attr, 1850 &dev_attr_comp_algorithm.attr, 1851 #ifdef CONFIG_ZRAM_WRITEBACK 1852 &dev_attr_backing_dev.attr, 1853 &dev_attr_writeback.attr, 1854 &dev_attr_writeback_limit.attr, 1855 &dev_attr_writeback_limit_enable.attr, 1856 #endif 1857 &dev_attr_io_stat.attr, 1858 &dev_attr_mm_stat.attr, 1859 #ifdef CONFIG_ZRAM_WRITEBACK 1860 &dev_attr_bd_stat.attr, 1861 #endif 1862 &dev_attr_debug_stat.attr, 1863 NULL, 1864 }; 1865 1866 static const struct attribute_group zram_disk_attr_group = { 1867 .attrs = zram_disk_attrs, 1868 }; 1869 1870 static const struct attribute_group *zram_disk_attr_groups[] = { 1871 &zram_disk_attr_group, 1872 NULL, 1873 }; 1874 1875 /* 1876 * Allocate and initialize new zram device. the function returns 1877 * '>= 0' device_id upon success, and negative value otherwise. 1878 */ 1879 static int zram_add(void) 1880 { 1881 struct zram *zram; 1882 struct request_queue *queue; 1883 int ret, device_id; 1884 1885 zram = kzalloc(sizeof(struct zram), GFP_KERNEL); 1886 if (!zram) 1887 return -ENOMEM; 1888 1889 ret = idr_alloc(&zram_index_idr, zram, 0, 0, GFP_KERNEL); 1890 if (ret < 0) 1891 goto out_free_dev; 1892 device_id = ret; 1893 1894 init_rwsem(&zram->init_lock); 1895 #ifdef CONFIG_ZRAM_WRITEBACK 1896 spin_lock_init(&zram->wb_limit_lock); 1897 #endif 1898 queue = blk_alloc_queue(zram_make_request, NUMA_NO_NODE); 1899 if (!queue) { 1900 pr_err("Error allocating disk queue for device %d\n", 1901 device_id); 1902 ret = -ENOMEM; 1903 goto out_free_idr; 1904 } 1905 1906 /* gendisk structure */ 1907 zram->disk = alloc_disk(1); 1908 if (!zram->disk) { 1909 pr_err("Error allocating disk structure for device %d\n", 1910 device_id); 1911 ret = -ENOMEM; 1912 goto out_free_queue; 1913 } 1914 1915 zram->disk->major = zram_major; 1916 zram->disk->first_minor = device_id; 1917 zram->disk->fops = &zram_devops; 1918 zram->disk->queue = queue; 1919 zram->disk->queue->queuedata = zram; 1920 zram->disk->private_data = zram; 1921 snprintf(zram->disk->disk_name, 16, "zram%d", device_id); 1922 1923 /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */ 1924 set_capacity(zram->disk, 0); 1925 /* zram devices sort of resembles non-rotational disks */ 1926 blk_queue_flag_set(QUEUE_FLAG_NONROT, zram->disk->queue); 1927 blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, zram->disk->queue); 1928 1929 /* 1930 * To ensure that we always get PAGE_SIZE aligned 1931 * and n*PAGE_SIZED sized I/O requests. 1932 */ 1933 blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE); 1934 blk_queue_logical_block_size(zram->disk->queue, 1935 ZRAM_LOGICAL_BLOCK_SIZE); 1936 blk_queue_io_min(zram->disk->queue, PAGE_SIZE); 1937 blk_queue_io_opt(zram->disk->queue, PAGE_SIZE); 1938 zram->disk->queue->limits.discard_granularity = PAGE_SIZE; 1939 blk_queue_max_discard_sectors(zram->disk->queue, UINT_MAX); 1940 blk_queue_flag_set(QUEUE_FLAG_DISCARD, zram->disk->queue); 1941 1942 /* 1943 * zram_bio_discard() will clear all logical blocks if logical block 1944 * size is identical with physical block size(PAGE_SIZE). But if it is 1945 * different, we will skip discarding some parts of logical blocks in 1946 * the part of the request range which isn't aligned to physical block 1947 * size. So we can't ensure that all discarded logical blocks are 1948 * zeroed. 1949 */ 1950 if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE) 1951 blk_queue_max_write_zeroes_sectors(zram->disk->queue, UINT_MAX); 1952 1953 zram->disk->queue->backing_dev_info->capabilities |= 1954 (BDI_CAP_STABLE_WRITES | BDI_CAP_SYNCHRONOUS_IO); 1955 device_add_disk(NULL, zram->disk, zram_disk_attr_groups); 1956 1957 strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor)); 1958 1959 zram_debugfs_register(zram); 1960 pr_info("Added device: %s\n", zram->disk->disk_name); 1961 return device_id; 1962 1963 out_free_queue: 1964 blk_cleanup_queue(queue); 1965 out_free_idr: 1966 idr_remove(&zram_index_idr, device_id); 1967 out_free_dev: 1968 kfree(zram); 1969 return ret; 1970 } 1971 1972 static int zram_remove(struct zram *zram) 1973 { 1974 struct block_device *bdev; 1975 1976 bdev = bdget_disk(zram->disk, 0); 1977 if (!bdev) 1978 return -ENOMEM; 1979 1980 mutex_lock(&bdev->bd_mutex); 1981 if (bdev->bd_openers || zram->claim) { 1982 mutex_unlock(&bdev->bd_mutex); 1983 bdput(bdev); 1984 return -EBUSY; 1985 } 1986 1987 zram->claim = true; 1988 mutex_unlock(&bdev->bd_mutex); 1989 1990 zram_debugfs_unregister(zram); 1991 1992 /* Make sure all the pending I/O are finished */ 1993 fsync_bdev(bdev); 1994 zram_reset_device(zram); 1995 bdput(bdev); 1996 1997 pr_info("Removed device: %s\n", zram->disk->disk_name); 1998 1999 del_gendisk(zram->disk); 2000 blk_cleanup_queue(zram->disk->queue); 2001 put_disk(zram->disk); 2002 kfree(zram); 2003 return 0; 2004 } 2005 2006 /* zram-control sysfs attributes */ 2007 2008 /* 2009 * NOTE: hot_add attribute is not the usual read-only sysfs attribute. In a 2010 * sense that reading from this file does alter the state of your system -- it 2011 * creates a new un-initialized zram device and returns back this device's 2012 * device_id (or an error code if it fails to create a new device). 2013 */ 2014 static ssize_t hot_add_show(struct class *class, 2015 struct class_attribute *attr, 2016 char *buf) 2017 { 2018 int ret; 2019 2020 mutex_lock(&zram_index_mutex); 2021 ret = zram_add(); 2022 mutex_unlock(&zram_index_mutex); 2023 2024 if (ret < 0) 2025 return ret; 2026 return scnprintf(buf, PAGE_SIZE, "%d\n", ret); 2027 } 2028 static CLASS_ATTR_RO(hot_add); 2029 2030 static ssize_t hot_remove_store(struct class *class, 2031 struct class_attribute *attr, 2032 const char *buf, 2033 size_t count) 2034 { 2035 struct zram *zram; 2036 int ret, dev_id; 2037 2038 /* dev_id is gendisk->first_minor, which is `int' */ 2039 ret = kstrtoint(buf, 10, &dev_id); 2040 if (ret) 2041 return ret; 2042 if (dev_id < 0) 2043 return -EINVAL; 2044 2045 mutex_lock(&zram_index_mutex); 2046 2047 zram = idr_find(&zram_index_idr, dev_id); 2048 if (zram) { 2049 ret = zram_remove(zram); 2050 if (!ret) 2051 idr_remove(&zram_index_idr, dev_id); 2052 } else { 2053 ret = -ENODEV; 2054 } 2055 2056 mutex_unlock(&zram_index_mutex); 2057 return ret ? ret : count; 2058 } 2059 static CLASS_ATTR_WO(hot_remove); 2060 2061 static struct attribute *zram_control_class_attrs[] = { 2062 &class_attr_hot_add.attr, 2063 &class_attr_hot_remove.attr, 2064 NULL, 2065 }; 2066 ATTRIBUTE_GROUPS(zram_control_class); 2067 2068 static struct class zram_control_class = { 2069 .name = "zram-control", 2070 .owner = THIS_MODULE, 2071 .class_groups = zram_control_class_groups, 2072 }; 2073 2074 static int zram_remove_cb(int id, void *ptr, void *data) 2075 { 2076 zram_remove(ptr); 2077 return 0; 2078 } 2079 2080 static void destroy_devices(void) 2081 { 2082 class_unregister(&zram_control_class); 2083 idr_for_each(&zram_index_idr, &zram_remove_cb, NULL); 2084 zram_debugfs_destroy(); 2085 idr_destroy(&zram_index_idr); 2086 unregister_blkdev(zram_major, "zram"); 2087 cpuhp_remove_multi_state(CPUHP_ZCOMP_PREPARE); 2088 } 2089 2090 static int __init zram_init(void) 2091 { 2092 int ret; 2093 2094 ret = cpuhp_setup_state_multi(CPUHP_ZCOMP_PREPARE, "block/zram:prepare", 2095 zcomp_cpu_up_prepare, zcomp_cpu_dead); 2096 if (ret < 0) 2097 return ret; 2098 2099 ret = class_register(&zram_control_class); 2100 if (ret) { 2101 pr_err("Unable to register zram-control class\n"); 2102 cpuhp_remove_multi_state(CPUHP_ZCOMP_PREPARE); 2103 return ret; 2104 } 2105 2106 zram_debugfs_create(); 2107 zram_major = register_blkdev(0, "zram"); 2108 if (zram_major <= 0) { 2109 pr_err("Unable to get major number\n"); 2110 class_unregister(&zram_control_class); 2111 cpuhp_remove_multi_state(CPUHP_ZCOMP_PREPARE); 2112 return -EBUSY; 2113 } 2114 2115 while (num_devices != 0) { 2116 mutex_lock(&zram_index_mutex); 2117 ret = zram_add(); 2118 mutex_unlock(&zram_index_mutex); 2119 if (ret < 0) 2120 goto out_error; 2121 num_devices--; 2122 } 2123 2124 return 0; 2125 2126 out_error: 2127 destroy_devices(); 2128 return ret; 2129 } 2130 2131 static void __exit zram_exit(void) 2132 { 2133 destroy_devices(); 2134 } 2135 2136 module_init(zram_init); 2137 module_exit(zram_exit); 2138 2139 module_param(num_devices, uint, 0); 2140 MODULE_PARM_DESC(num_devices, "Number of pre-created zram devices"); 2141 2142 MODULE_LICENSE("Dual BSD/GPL"); 2143 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>"); 2144 MODULE_DESCRIPTION("Compressed RAM Block Device"); 2145